JACKSONVILLE, Fla. -- For one First Coast teenager, life was over before it really began.

Sentenced at 15 to life without in prison for killing a man he said raped him, Mark Berrios has lived the majority of his life behind bars.

But a Supreme Court decision could put him out of prison, and into an adult world he barely knows.

Kaitlyn Ross sat down with Berrios at the Northwest Reception Center Prison to talk about the road ahead.

Freedom is just a memory for Mark Berrios.

"I remember the grass being green, and the change of the seasons, being outside on a rainy day," he said.

In prison for the past 18 years, Berrios has been locked up longer than he was ever free.

Growing up in Jacksonville, he had an older brother and sister, a family who loved him.

But he said one decision changed all that.

He was sentenced to life without parole at 15 years old, and still dreams about what it was like on the outside.

"I still have those memories, I keep those memories, I cherish those memories. I want to make more," he said.

In 18 years, he's been locked up in five different prisons.

He passes the time by tutoring other inmates in math, and helping them get their GEDs.

The work is tedious, and the days go by slowly.

"It's like Groundhog Day. It's the same thing over and over and over," he said.

It gives him a lot of time to think about why he's there.

Berrios was just 14 when he ran away from home.

He was picked up near Daytona by a 41-year-old man named Olen Hepler.

Hepler took him in, gave him alcohol, and left him alone ... for the first week.

Then Berrios said Hepler started molesting him.

"It's not something my mom ever talked to me about. So I was in that situation and I didn't know what to do. I didn't have an escape plan, I didn't have a forethought of what was going to happen. And as it was going on, I panicked, I was scared," he said.

Berrios said he's in prison because he finally fought back.

"I did what I thought I had to, that's when I grabbed his gun. I grabbed it and he grabbed the front, I had the gun in my hands, and I pulled the trigger," he said.

After he shot Hepler, he stole his car and drove back to Jacksonville.

Berrios never denied the killing when the cops showed up, but he never thought he would be tried for the crime, self-defense.

"I understand it now, but then ... It was almost like a nightmare, it was a nightmare come true. It was like, it's hard to explain. It was like the impossible happened," he said.

At 15 years old, he turned down a plea deal to spend 19 years in prison.

When he took his chances on a trial, he was convicted of first-degree murder, and a mandatory sentence of life without parole.

He still struggles to explain what happened to his mother and grandfather when they visit.

"I don't know how they're looking at me. If they look at me like this is something I wasn't supposed to do and they're not telling me, or I did something I was supposed to do, and now I'm suffering the consequences," he said.

While his biggest fear is what he looks like through their eyes, he seems helpless to change it.

After nearly two decades behind bars, he says he'll take whatever judgment the people he loves see fit.

"That's not up to me to decide. I don't want to decide my own fate," he said.

A recent Supreme Court decision may change that.

In June, the panel ruled sentencing minors to mandatory life without parole was inhumane, and ordered that the practice stop immediately.

Berrios heard the news in his jail cell.

"Just a little tidbit. And I listened to the radio all day. Just that little 10 second update all day long. I couldn't believe it," he said.

Now the question is whether or not the ruling will be retroactive.

There are about 1,000 people in the United States who were sentenced to life without parole as minors waiting to see if they'll get another day in court.

The lower courts have split on the issue.

One young man in Jacksonville just had his life sentenced overturned, in line with the Supreme Court ruling, but the judge in Berrios' case told his lawyer he wanted to wait and see what other courts did with the decision before he ruled.

Even though he doesn't have an answer yet, Berrios said the news has changed his life.

"There was nothing before this. Before this, there was just hope. Now there's something to hope for. And that's two totally different things in your mind: hoping and having something to hope for. Now I have something to hope for," he said.

If they get another day in court, his lawyer is hoping a judge will hear new evidence in the case.

A lawyer who represented Hepler before he was killed has come forward with a sworn statement that his client had sexually molested other young boys.

And an FBI investigation into those charges was never admitted in to Berrios' first trial.

Right now there are a lot of questions about how the case will proceed, and it weighs on Berrios every day.

"Looking back, it feels like I just came to prison, like, a year ago. But looking forward it's like oh God, another week, another month, another year. It's hard to have hope, and then have hope put off. It's not easy at all," he said.

And even after all these years, he still can't imagine living the rest of his life in prison.

"To ask me what it looks like, I don't know, I don't think I'm going to find out," he said.

Berrios has been granted another hearing in his case, but no date has been set yet.